If Scim is used it is likely that setting up alternative keyboard isn't required. However, there are some exceptions, notably Arabic.

Some languages require a different keyboard layout to work properly. The default US layout has only a limited number of characters, which is adequate for English but not for languages which have diacritical marks (commonly known as accents). This covers most other languages using Latin characters.

A different keyboard layout can be set as default. If different layouts are going to be used at different times it is easy to set up two (or more) layouts and switch between them.

</blockquote>
<p>
You'll see a window like this:<br />
<br />
<a href="http://img201.imageshack.us/img201/4473/xkbconfigopt.png"><span class="inline inline-left"><img src="http://img201.imageshack.us/img201/4473/xkbconfigopt.png" class="image-ia image-_original" height="431" width="340" /></span></a>
<br />
<p>
There are four things we are going to change, and one of those is optional. They are marked in red.
</p>
<br />
<h2>Group Shift/Lock behaviour</h2>
<br />
This sets the key combination you use to switch keyboard layouts.
<p>
It's a rather confusing option. The name doesn't really tell you what it does. Also, when you actually click on this button, you see a large number of options - and many of them look rather similar.
</p>
<p>
<a href="http://img190.imageshack.us/img190/8151/xkbconfiggrsh.png"><span class="inline inline-left"><img src="http://img190.imageshack.us/img190/8151/xkbconfiggrsh.png" class="image-ia image-_original" height="374" width="532" /></span></a>
</p>
<p>
In the screenshot I've select the one that I use. That lets me switch layouts at any time by pressing shift and alt. (Shift needs to be the first one pressed or nothing happens.)
</p>
<p>
I've chosen this combination because many of the other options are already used for another function. Control-shift is used a lot for keyboard shortcuts, for example. If you prefer something else, you have quite a few choices.
</p>
<p>
<br />
<h2>Third level choosers</h2>
</p>
<p>
When you press this key at the same time as another, you are able to enter a range of special characters. (If you have a US keyboard layout, it doesn't do anything.)
</p>
<p>
I've chosen "any of the win keys" because I don't use them for anything else. (It's good to know they are of <i>some</i> use on a Linux system. :) ) It's the one selected in the screenshot.
</p>
<p>
<a href="http://img219.imageshack.us/img219/6250/xkbconfig3lvl.png"><span class="inline inline-left"><img src="http://img219.imageshack.us/img219/6250/xkbconfig3lvl.png" class="image-ia image-_original" height="364" width="463" /></span></a>
</p>
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